Thermochromic dye, preparation and use thereof

Abstract

The application discloses a thermochromic dye and a preparation and application thereof, and belongs to the technical field of fine chemical industry. The application firstly introduces amino groups into a fluoran dye structure by using the reaction between a lactone and an alkyl diamine with the fluoran dye as raw material; and then, the aldehyde amine reaction between the amino fluoran dye and phenolic hydroxyl benzaldehyde is utilized to prepare a lactam thermochromic dye. The application utilizes the characteristics that the phenolic hydroxyl in the structure of the thermochromic dye releases protons at low temperature and obtains protons at high temperature, and utilizes the flexibility of the alkyl chain in the structure of the alkyl diamine, so that the ring-opening and ring-closing reactions of the lactam structure in the fluoran dye structure are caused, the size of the conjugated system of the dye is adjusted, and the color change of the dye is realized.

Description

Technical Field

[0001] This invention relates to a thermochromic dye, its preparation and application, and belongs to the field of fine chemical technology. Background Technology

[0002] There are many types of thermochromic materials. Fluorane thermochromic materials can control their color by changing the electron-donating and electron-withdrawing properties, quantity and position of their substituents. They have become the mainstream thermosensitive materials and are widely used in temperature-indicating coatings, color-changing inks, anti-counterfeiting and many other fields.

[0003] Fluorescein-based thermochromic materials generally consist of three components: a fluorane dye, a color developer, and a phase change material. The fluorane dye acts as the color developer, an electron-donating substance in the thermochromic system. It donates electrons to the color developer, thus determining the color of the system. The color developer is the compound that causes the thermochromic reaction; it accepts electrons donated by the color developer, causing a color change and determining whether and how intense the color change occurs. The melting point of the phase change material determines the thermochromic temperature of the system.

[0004] The color-changing principle of this conventional thermochromic dye (i.e., a three-component system) is as follows.

[0005]

[0006] During the heating process, when the external temperature reaches the melting temperature of the phase change material, the phase change material is in a solution state, capable of dissolving the leuco and chromophore. Both exist as independent molecules, and their interaction is disrupted by the solvent. The central carbon atom of the leuco forms a ring, becoming sp. 3 The hybrid tetrahedral structure exhibits poor molecular planarity and disrupts the conjugated system, resulting in a colorless overall system. During the cooling process, when the external temperature drops to the crystallization temperature of the phase change material, the material enters a solid state. The chromogenic and leuco components interact strongly, undergoing electron interconversion, opening the lactone ring, and transforming the central carbon atom into an sp atom. 2 The hybrid orbitals, forming a large π-conjugated structure, enable the dye to absorb light in the visible region.

[0007] As can be seen from the above color-changing principle, the electron transfer rate between the chromophore and the developer affects the color-changing sensitivity, i.e., the color-changing response time, of the system. Currently, existing fluorane color-changing systems are generally three-component systems, and the electron transfer between the chromophore and the developer is often intermolecular electron transfer, resulting in a low electron transfer rate. For example, CN112852402A describes the preparation of a thermochromic material for textile printing using crystal violet lactone as the chromophore, bisphenol A as the developer, and alkyl alcohol as the phase change material. CN115785599A describes the preparation of a biomimetic thermochromic material for hyperspectral camouflage using dyes such as 16(3,3-bis(N-octyl-2-methylindole)phthalic acid lactone) as chromogenic agents, bisphenol A as a chromogenic agent, and phenyl alcohol ((2-(4-phenylmethoxy)ethanol) as a phase change material). CN115888572A describes the preparation of a color-changing material with multi-gamut indication and temperature-regulating functions using crystal violet lactone and weakly acidic dyes as chromogenic agents, bisphenol A as a chromogenic agent, and alcohol esters as phase change materials. Summary of the Invention

[0008] [Technical Issues]

[0009] Currently, most existing thermochromic dyes are three-component systems consisting of a chromophore, a developer, and a phase change material. The color change occurs due to intramolecular electron transfer between the chromophore and the chromosome. However, the low rate of intramolecular electron transfer affects the color change sensitivity of the system, thus impacting its application performance.

[0010] [Technical Solution]

[0011] To address the aforementioned issues, this invention prepares a thermochromic dye capable of intramolecular electron transfer, which can significantly improve the electron transfer rate of the color-changing system, thereby significantly enhancing the system's color-changing sensitivity. Furthermore, since the color-changing system is transformed from a three-component system to a two-component system, the color-changing system is simpler, and the color-changing performance is more stable and controllable.

[0012] This invention first uses fluorane dyes as raw materials and introduces an amino group into the fluorane dye structure through the reaction between lactones and alkyl diamines. Then, it utilizes the aldehyde-amine reaction between the amino-fluorane dye and phenolic hydroxybenzaldehyde to prepare a lactam thermochromic dye. This invention leverages the property of the phenolic hydroxyl group in the thermochromic dye structure to release protons at low temperatures and gain protons at high temperatures, and utilizes the flexibility of the alkyl chain in the alkyl diamine structure to allow the lactam structure in the fluorane dye to undergo ring-opening and ring-closing reactions, adjusting the size of the dye's conjugated system to achieve color change. The color-changing mechanism of the lactam thermochromic dye of this invention is as follows:

[0013]

[0014] The first objective of this invention is to provide a thermochromic dye with the following structural formula:

[0015]

[0016] In the formula:

[0017] n is 1-17;

[0018] R1 and R2 are each independently selected from: -H, C1-6 alkyl, substituted or unsubstituted phenyl;

[0019] R3 and R4 are independently selected from: -H, halogen (F, Cl, Br, I), C1-6 alkyl, halo-C1-6 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted phenylamino.

[0020] R5, R6, R7 and R8 are each independently selected from -H, -OH, and at least one of them is -OH;

[0021] The substituents on the phenyl group can be: halogens (F, Cl, Br, I), C1-6 alkyl groups, or halogenated C1-6 alkyl groups.

[0022] In one embodiment of the present invention, the substituent on the phenyl group is monosubstituted, disubstituted, trisubstituted, or tetrasubstituted.

[0023] In one embodiment of the present invention, R1 and R2 are independently selected from: -H, -CH3, -C2H5, n-C3H7, i-C4H9, n-C4H9, n-C5H 11 ,

[0024] In one embodiment of the present invention, R3 and R4 are independently selected from: -H, Cl, -CH3, -C2H5, n-C4H9, n-C5H 11 ,

[0025] In one embodiment of the present invention, R5 and R8 are -OH, and R6, R7 are H; or R8 is -OH, and R5, R6, R7 are H.

[0026] In one embodiment of the present invention, n is further 6-9.

[0027] A second objective of this invention is to provide a method for producing thermochromic dyes, comprising the following steps:

[0028] (1) First, weigh a certain amount of fluorane dye and ethanol, heat to 80°C and stir until completely dissolved; then add a certain amount of diamine compound, reflux for a certain time, and evaporate to dryness; finally, extract the amination dye with an aqueous solution of dichloromethane and ethanol, and dry to obtain the amination dye.

[0029] (2) Weigh a certain amount of hydroxybenzaldehyde compound and dissolve it in a certain amount of chloroform. Cool it down to 0°C, add a certain amount of anhydrous aluminum chloride, and stir for a certain time at room temperature to obtain a hydroxybenzaldehyde solution.

[0030] (3) Weigh a certain amount of amination dye, triethylamine and chloroform, stir until completely dissolved, and slowly add dropwise to the above hydroxybenzaldehyde solution. Continue stirring for a certain time at room temperature, add alkali to terminate the reaction, and the layering phenomenon occurs. Extract the aqueous layer with dichloromethane and recrystallize it in methanol solution to obtain thermochromic dye.

[0031] In one embodiment of the present invention, the structure of the fluorane dye in step (1) is as follows:

[0032]

[0033] The definitions of R1-R4 are the same as above.

[0034] In one embodiment of the present invention, the diamine compound in step (1) is: ethylenediamine, propylenediamine, diethylenetriamine, butanediamine, pentanediamine, hexanediamine, decanediamine, dodecanediamine, tetradecanediamine, hexadecanediamine, or octadecanediamine.

[0035] In one embodiment of the present invention, the molar ratio of fluorane dye and diamine compound in step (1) is 1:(15-40).

[0036] In one embodiment of the present invention, the mass ratio of fluorane dye to ethanol in step (1) is 1:(10-50).

[0037] In one embodiment of the present invention, the reflux time in step (1) is 4 to 36 hours.

[0038] In one embodiment of the present invention, the mass ratio of ethanol to water in the aqueous solution of ethanol in step (1) is 1:(0.1 to 10).

[0039] In one embodiment of the present invention, the structure of the hydroxybenzaldehyde compound in step (2) is as follows:

[0040]

[0041] The definitions of R5, R6, R7, and R8 are the same as above.

[0042] In one embodiment of the present invention, the molar ratio of the amination dye and the hydroxybenzaldehyde compound in step (2) is 1:(1 to 1.1).

[0043] In one embodiment of the present invention, the mass ratio of hydroxybenzaldehyde compound to chloroform in step (2) is 1:(30-60).

[0044] In one embodiment of the present invention, the molar ratio of hydroxybenzaldehyde compound to anhydrous aluminum chloride in step (2) is 1:(1-1.5).

[0045] In one embodiment of the present invention, the stirring time in step (2) is 4 to 10 hours.

[0046] In one embodiment of the present invention, the molar ratio of the amination dye to the hydroxybenzaldehyde compound in step (3) is 1:1.

[0047] In one embodiment of the present invention, the molar ratio of the amination dye to triethylamine in step (3) is 1:(2-5).

[0048] In one embodiment of the present invention, the mass ratio of the amination dye to chloroform in step (3) is 1:(10-15).

[0049] In one embodiment of the present invention, the stirring reaction time in step (3) is 6 to 15 hours.

[0050] The third objective of this invention is the application of the thermochromic dyes described herein in textile dyeing, printing, and spinning.

[0051] In one embodiment of the present invention, the textile includes polyester, nylon, cotton, viscose, linen or a variety of blended fibers and their fabrics.

[0052] In one embodiment of the present invention, the thermochromic fabric is obtained by dyeing, printing or spinning fibers with thermochromic dyes.

[0053] [Beneficial Effects]

[0054] The thermochromic dye of this invention solves the problems of "poor color change sensitivity caused by intermolecular electron transfer and poor color change controllability of complex three-component systems in existing thermochromic dyes", and expands its application in the direction of high sensitivity color change and color change controllability. Detailed Implementation

[0055] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0056] The fluorane dyes used in the following examples are available from Wuhan Shuer Biotechnology Co., Ltd., and their structures are shown below:

[0057]

[0058] Test method:

[0059] 1. Nuclear magnetic resonance hydrogen spectrum (NMR)1 H-NMR):

[0060] Deuterated chloroform was used as the solvent, and the samples were characterized by nuclear magnetic resonance spectroscopy using an AVANCE III instrument.

[0061] 2. Temperature-induced color change sensitivity test:

[0062] Weigh 3g of the colored material and add it to the tablet press, flatten it, and place it in a petri dish. Set the temperature control platform to 50℃, place the petri dish on the platform, and record the temperature rise and color change of the material from colored to colorless, recording the time for complete decolorization.

[0063] 3. Temperature-induced color change sensitivity test:

[0064] Weigh 3g of the color-changing material and add it to the tablet press to flatten it. Place it in a petri dish and heat it to 60℃. The color-changing material will then appear colorless. Set the temperature control platform to 50℃ and place the petri dish on the platform. Record the cooling and color change process of the material as it changes from colorless to colored, and record the time for complete recoloring.

[0065] Example 1

[0066] A method for preparing thermochromic dyes includes the following steps:

[0067] (1) Weigh 0.01 mol of fluorane dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80 °C and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 h and evaporate to dryness; finally extract the amination dye with a mixture of dichloromethane and ethanol aqueous solution (ethanol and water mass ratio of 1:0.1), and dry to obtain the amination dye.

[0068] (2) Weigh 0.01 mol of p-hydroxybenzaldehyde (M = 122.12, 1.22 g) and dissolve it in 60 g of chloroform. Cool the solution to 0 °C and add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g). Stir the solution at room temperature for 7 h.

[0069] (3) Weigh 0.01 mol of amination dye (M = 556.5 g, 5.57 g), 0.03 mol of triethylamine (M = 101.19 g, 3.04 g), and 60 g of chloroform. Stir until completely dissolved, and slowly add the mixture dropwise to the above p-hydroxybenzaldehyde solution. Continue stirring at room temperature for 10 h. Terminate the reaction by adding 1 mol / L sodium hydroxide solution, resulting in layer separation. Extract the aqueous layer with dichloromethane and recrystallize it in methanol solution to obtain the thermochromic dye.

[0070] The structural formula of the obtained thermochromic dye is as follows:

[0071]

[0072] The synthesis steps of thermochromic dyes are as follows:

[0073]

[0074] The structure is characterized as follows:

[0075] 1 H-NMR (400MHz, CHCl3-d6): δ8.76 (s, 1H, N=C H ), δ7.91 (d, 2H, Ar-H), 7.78 (d, 2H, Ar-H), 7.58 (t, 1H, Ar-H), 7.18 (t, 1H, Ar-H), 7.10 (s, 1H, Ar-H), 7.00 (s, 1H, Ar -H), 6.85 (d, 2H, Ar-H), 6.54 (d, 1H, Ar-H), 6.38 (d, 1H, Ar-H), 6.34 (s, 1H, Ar-H), 5.35 (s, 1H, OH), 3.41 (q, 4H, -NC H 2CH3), 3.20(q, 4H, NC) H 2CH2), 2.34(s, 3H, C) H 3), 1.59-1.65 (m, 4H, NCH2C) H 2), 1.29 (s, 12H, C) H 2), 1.15(s, 6H, C) H 3).

[0076] Example 2

[0077] A method for preparing thermochromic dyes includes the following steps:

[0078] (1) Weigh 0.01 mol of fluorane dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80 °C and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 h and evaporate to dryness; finally extract the amination dye with a mixture of dichloromethane and ethanol aqueous solution (ethanol and water mass ratio of 1:0.1), and dry to obtain the amination dye.

[0079] (2) Weigh 0.01 mol of 2,5-dihydroxybenzaldehyde (M = 138.12, 1.38 g) and dissolve it in 65 g of chloroform. Cool the solution to 0 °C and add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g). Stir the solution at room temperature for 7 h.

[0080] (3) Weigh 0.01 mol of amination dye (M = 556.5 g, 5.57 g), 0.03 mol of triethylamine (M = 101.19 g, 3.04 g), and 60 g of chloroform. Stir until completely dissolved, and slowly add the mixture dropwise to the above p-hydroxybenzaldehyde solution. Continue stirring at room temperature for 10 h. Terminate the reaction by adding 1 mol / L sodium hydroxide solution, resulting in layer separation. Extract the aqueous layer with dichloromethane and recrystallize it in methanol solution to obtain the thermochromic dye.

[0081] The structural formula of the obtained thermochromic dye is as follows:

[0082]

[0083] The synthesis steps of thermochromic dyes are as follows:

[0084]

[0085] The structure is characterized as follows:

[0086] 1 H-NMR (400MHz, CHCl3-d6): δ8.56 (s, 1H, N=C H ), δ7.91 (d, 2H, Ar-H), 7.58 (t, 1H, Ar-H), 7.29 (s, 1H, Ar-H), 7.18 (t, 1H, Ar-H), 7.10 (s, 1H, Ar-H), 7.00 (s, 1H, Ar -H), 6.85 (d, 2H, Ar-H), 6.54 (d, 1H, Ar-H), 6.38 (d, 1H, Ar-H), 6.34 (s, 1H, Ar-H), 5.35 (s, 1H, OH), 3.41 (q, 4H, -NC H 2CH3), 3.20(q, 4H, NC) H 2CH2), 2.34(s, 3H, C) H 3), 1.59-1.65 (m, 4H, NCH2C) H 2), 1.29 (s, 12H, C) H 2), 1.15(s, 6H, C) H 3).

[0087] Comparative Example 1

[0088] The structure of a simple fluorane dye (commercially available) is shown below:

[0089]

[0090] Comparative Example 2

[0091] A method for preparing thermochromic dyes includes the following steps:

[0092] (1) Weigh 0.01 mol of fluorane dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80 °C and stir until completely dissolved; then add 0.36 mol of ethylenediamine (M = 60.1, 21.64 g), reflux for 24 h and evaporate to dryness; finally extract the amination dye with a mixture of dichloromethane and ethanol aqueous solution (ethanol and water mass ratio of 1:0.1), and dry to obtain the amination dye.

[0093] (2) Weigh 0.01 mol of p-hydroxybenzaldehyde (M = 122.12, 1.22 g) and dissolve it in 70 g of chloroform. Cool the solution to 0 °C and add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g). Stir the solution at room temperature for 7 h.

[0094] (3) Weigh 0.01 mol of amination dye (M = 556.5, 5.57 g), 0.03 mol of triethylamine (M = 101.19, 3.04 g), and 60 g of chloroform. Stir until completely dissolved, and slowly add the mixture dropwise to the above p-hydroxybenzaldehyde solution. Continue stirring at room temperature for 10 h. Add 1 mol / L sodium hydroxide to terminate the reaction, and layering occurs. Extract the aqueous layer with dichloromethane and recrystallize it in methanol solution to obtain the thermochromic dye.

[0095] The structural formula of the obtained thermochromic dye is as follows:

[0096]

[0097] Comparative Example 3

[0098] A method for preparing thermochromic dyes includes the following steps:

[0099] (1) Weigh 0.01 mol of fluorane dye (M = 402.5, 4.03 g) and 60 g of ethanol, heat to 80 °C and stir until completely dissolved; then add 0.36 mol of decanediamine (M = 174, 62.6 g), reflux for 24 h and evaporate to dryness; finally extract the amination dye with a mixture of dichloromethane and ethanol aqueous solution (ethanol and water mass ratio of 1:0.1), and dry to obtain the amination dye.

[0100] (2) Weigh 0.01 mol of 3,5-dibromo-4-hydroxybenzaldehyde (M = 279.91, 2.80 g) and dissolve it in 60 g of chloroform. Cool the mixture to 0 °C and add 0.012 mol of anhydrous aluminum chloride (M = 122.12, 1.68 g). Stir the mixture at room temperature for 7 h.

[0101] (3) Weigh 0.01 mol of amination dye (M = 556.5 g, 5.57 g), 0.035 mol of triethylamine (M = 101.19 g, 3.54 g), and 65 g of chloroform. Stir until completely dissolved, and slowly add the mixture dropwise to the above p-hydroxybenzaldehyde solution. Continue stirring at room temperature for 10 h. Add 1 mol / L sodium hydroxide to terminate the reaction, and layering occurs. Extract the aqueous layer with dichloromethane and recrystallize it in methanol solution to obtain the thermochromic dye.

[0102] The structural formula of the obtained thermochromic dye is as follows:

[0103]

[0104] Color change sensitivity test:

[0105] Example 1 and Example 2 were melt-blended with phase change material cetyl alcohol (mass ratio 1:24) at 80°C, cooled to room temperature, and the color change response time of the dye at 50°C was tested.

[0106] Comparative Example 1, bisphenol A, and phase change material cetyl alcohol (mass ratio 1:2:24) were melt-blended at 80°C, cooled to room temperature, and the color change response time of the dye at 50°C was tested.

[0107] The specific test results are shown in Table 1.

[0108] Table 1. Color change in the examples and comparative examples.

[0109] sample Color change Temperature-induced color change response time Cooling and color change response time Example 1 + Cetyl alcohol system The red color turns colorless. 15s 56s Example 2 + Cetyl alcohol system The red color turns colorless. 29s 42s Comparative Example 1 + Bisphenol A + Cetyl alcohol system The red color turns colorless. 50s 120s Comparative Example 1 + Cetyl alcohol system The red color remains unchanged. -- -- Comparative Example 2 + Cetyl alcohol system The red color remains unchanged. -- -- Comparative Example 3 + Cetyl alcohol system The red color remains unchanged. -- --

[0110] As shown in the table, when the chromophore is Comparative Example 1, the cooling and heating color-changing response times of the three-component color-changing system are 120 s and 50 s, respectively, indicating a relatively long color-changing response time. When the chromophores are Examples 1 and 2, both the cooling and heating color-changing response times are significantly shortened, and the color-changing sensitivity is significantly improved. Furthermore, when the chromophores are Comparative Examples 1, 2, and 3, the two-component color-changing system fails to achieve color change.

[0111] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A thermochromic dye, the structural formula of which is as follows: In the formula: R1 and R2 are independently selected from: -H, -CH3, -C2H5, n-C3H7, i-C4H9, n-C4H9, n-C5H 11 , or ; R3 and R4 are independently selected from: -H, Cl, -CH3, -C2H5, n-C4H9, n-C5H 11 , , , , or ; R5 and R8 are -OH, and R6 and R7 are H; or R8 is -OH, and R5, R6, and R7 are H; n is 6-9.

2. A method for preparing the thermochromic dye according to claim 1, characterized in that, Includes the following steps: (1) Fluorane dye and ethanol are mixed and heated and stirred until completely dissolved; then diamine compound is added, refluxed, and evaporated to dryness; finally, the amination dye is extracted with an aqueous solution of dichloromethane and ethanol and dried to obtain the amination dye; (2) Hydroxybenzaldehyde compounds are dissolved in chloroform, cooled to 0-5℃, anhydrous aluminum chloride is added, and stirred for a certain time at room temperature to obtain a hydroxybenzaldehyde solution. (3) Mix the amination dye, triethylamine and chloroform, stir until completely dissolved, and slowly add dropwise to the hydroxybenzaldehyde solution obtained in step (2). Continue stirring for a certain time at room temperature, add alkali to terminate the reaction, and the layering phenomenon occurs. The aqueous layer was extracted with dichloromethane and recrystallized in methanol solution to obtain a thermochromic dye.

3. The method according to claim 2, characterized in that, The structure of the fluorane dye in step (1) is as follows: The definitions of R1-R4 are the same as in claim 1.

4. The method according to claim 2, characterized in that, In step (1), the diamine compounds are: ethylenediamine, propylenediamine, diethylenetriamine, butanediamine, pentanediamine, hexanediamine, decanediamine, dodecanediamine, tetradecanediamine, hexadecanediamine, and octadecanediamine; the molar ratio of fluorane dye to diamine compound is 1:(15~40); the mass ratio of fluorane dye to ethanol is 1:(10~50).

5. The method according to claim 2, characterized in that, The structure of the hydroxybenzaldehyde compounds in step (2) is as follows: The definitions of R5, R6, R7 and R8 are the same as in claim 1.

6. The method according to claim 2, characterized in that, In step (2), the molar ratio of amination dye to hydroxybenzaldehyde compound is 1:(1~1.1); the mass ratio of hydroxybenzaldehyde compound to chloroform is 1:(30~60); and the molar ratio of hydroxybenzaldehyde compound to anhydrous aluminum chloride is 1:(1~1.5).

7. The method according to claim 2, characterized in that, In step (3), the molar ratio of the amination dye to the hydroxybenzaldehyde compound is 1:1; the molar ratio of the amination dye to triethylamine is 1:(2~5); and the mass ratio of the amination dye to chloroform is 1:(10~15).

8. The application of the thermochromic dye according to claim 1 in textile dyeing, printing and spinning.

9. A thermochromic fabric, characterized in that, It is obtained by dyeing, printing or spinning fibers using the thermochromic dye described in claim 1.

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